Microfluidic devices and systems are commonly used in the art for processing and/or analyzing of very small samples of fluids, such as samples in the 10 nl to about 5 ml size range. In such microfluidic devices and systems, the integration of many elements in a single microfluidic device has enabled the powerful and flexible analysis systems with applications ranging from cell sorting to protein synthesis. Some microfluidic operations that are functional to the performance of said applications include mixing, filtering, metering pumping reacting sensing heating and cooling of fluids in the microfluidic device.
Many different approaches have so far been explored for controlling said operations in a microfluidic environment, including combining thousands of lithographically defined components, such as pumps and valves, into chip based systems to achieve control over reagents concentrations and reactions' performance.
In particular, many different approaches have so far been explored for achieving thermal control in microfluidic devices, including the construction of resistive heating elements within fluidic chambers and immersing the entire chip into coolant. In particular, Applicants have described heating cooling devices for a microfluidic apparatus having a thermal insulating substrate in U.S. Pub. App. No. 2006/0288708, incorporated herein by reference in its entirety. In that application a Peltier device (i.e. a heating/cooling device having a Peltier junction) is located inside a microfluidic apparatus.